1. Field of the Invention
The present invention generally relates to a power steering system for a marine vessel and, more particularly, to a power steering system that incorporates an integrated steering cylinder and piston that is formed as an integral part of an outboard motor support structure.
2. Description of the Prior Art
It is a known procedure in the marine industry, particularly with outboard motors, to provide either manual hydraulic steering systems or power hydraulic steering systems in order to assist the operator of a marine vessel in causing the marine propulsion system to rotate about its steering axis. Most of the systems are provided as xe2x80x9caftermarketxe2x80x9d products that are added to the marine propulsion system after it is initially purchased. Some of these systems are provided by boat builders who combine a marine propulsion system purchased from one manufacturer with a hydraulic steering system or power steering system purchased from another supplier. In most cases, a steering cylinder is attached to the outboard motor to provide the necessary forces for causing the outboard motor to rotate about its steering axis in response to movement of a steering wheel by the operator of the marine vessel.
U.S. Pat. No. 6,402,577, which issued to Treinen et al. on Jun. 11, 2002, discloses an integrated hydraulic steering system for a marine propulsion unit. The steering system is provided in which a steering actuator is an integral portion of the support structure of the marine propulsion system. A steering arm is contained completely within the support structure of the marine propulsion system and is disposed about its steering axis. An extension of the steering arm extends into a sliding joint which has a linear component and a rotational component which allows the extension of the steering arm to move relative to a moveable second portion of the steering actuator. The moveable second portion of the steering actuator moves linearly within a cylinder cavity formed in a first portion of the steering actuator.
U.S. Pat. No. 6,276,977, which issued to Treinen et al. on Aug. 21, 2001, discloses an integrated hydraulic steering actuator. The actuator is provided for an outboard motor system in which the cylinder and piston of the actuator are disposed within a cylindrical cavity inside a cylindrical portion of a swivel bracket. The piston within the cylinder of the actuator is attached to at least one rod that extends through clearance holes of a clamp bracket and is connectable to a steering arm of an outboard motor. The one or more rods attached to the piston are aligned coaxially with an axis of rotation about which the swivel bracket rotates when the outboard motor is trimmed. As a result, no relative movement occurs between the outboard motor, the rod attached to the piston of the actuator, and the swivel bracket during rotation of the outboard motor about the axis of rotation.
U.S. Pat. No. 6,146,220, which issued to Alby et al. on Nov. 14, 2000, discloses a pedestal mount for an outboard motor. The outboard motor is mounted to a transom of a boat with a pedestal that is attached either directly to the transom or to an intermediate place that is, in turn, attached to the transom. A motor support platform is attached to the outboard motor, and a steering mechanism is attached to both pedestal and the motor support platform. The tilting mechanism is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilting axis relative to both the pedestal and the motor support platform. The tilting mechanism is rotatable relative to the pedestal and about a steering axis. The steering axis is generally vertical and stationary relative to the pedestal and is unaffected by the tilting of the outboard motor. The tilting mechanism is rotatable relative to the pedestal and about the steering axis with the outboard motor.
U.S. Pat. 6,183,321, which issued to Alby et al. on Feb. 6, 2001, discloses an outboard motor with a hydraulic pump and an electric motor located within a steering mechanism. The outboard motor comprises a pedestal that is attached to a transom of a boat, a motor support platform that is attached to the outboard motor, and a steering mechanism that is attached to both the pedestal and the motor support platform. It comprises a hydraulic tilting mechanism that is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilt axis relative to both the pedestal and the motor support platform. A hydraulic pump is connected in fluid communication with the hydraulic tilting mechanism to provide pressurized fluid to cause the outboard motor to rotate about its tilting axis. An electric motor is connected in torque transmitting relation with the hydraulic pump. Both the electric motor and the hydraulic pump are disposed within the steering mechanism.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Since the use of power steering systems in conjunction with outboard motors typically requires the addition of cylinders and pistons to exert the necessary forces to cause the outboard motor to rotate about its steering axis, it would be significantly beneficial if a power steering system could be provided for use in conjunction with a steering cylinder and piston that is incorporated as an internal component of the outboard motor support structure.
A marine propulsion system, made in accordance with the preferred embodiment of the present invention, comprises a support structure attachable to the marine propulsion system and to a marine vessel. The marine propulsion system is rotatable about a generally vertical steering axis and a generally horizontal tilting axis. A steering arm is attachable to the marine propulsion system and is rotatable about the steering axis. A steering actuator has a first portion attachable to the support structure and a second portion attached in force transmitting relation with the steering arm. The steering arm extends into the second portion. The second portion is moveable within the first portion. The first portion remains stationary with respect to the support structure during rotation of the marine propulsion system about either its steering axis or its tilting axis. The steering actuator is a hydraulic actuator. The first portion of the steering actuator comprises a hydraulic cylinder and a second portion of the steering actuator is a moveable piston within the first portion of the steering actuator in response to changes in hydraulic pressure between a first cavity and a second cavity of the hydraulic cylinder. A hydraulic pump is provided and has a pressurized outlet and a return inlet. A valve, which is connected in fluid communication between the hydraulic pump and the hydraulic cylinder, is responsive to movement of a steering device to control the flow of pressurized fluid from the hydraulic pump to the hydraulic cylinder and to control the flow of return fluid from the hydraulic cylinder to the hydraulic pump.
The steering device is a steering wheel of a marine vessel in a particularly preferred embodiment of the present invention. The first cavity of the hydraulic cylinder is disposed at a first side of the moveable piston and the second cavity of the hydraulic cylinder is disposed at a second side of the moveable piston. The moveable piston is disposed between the first and second cavities. The valve comprises a first conduit connected in fluid communication with the first cavity and the second conduit connected in fluid communication with the second cavity.
The support structure, steering arm, and steering actuator of the present invention is preferably made in accordance with the components described in U.S. Pat. No. 6,402,577. The interaction of the steering actuator, the moveable piston within the hydraulic cylinder, and the steering axis of the outboard motor are described in detail in U.S. Pat. No. 6,402,577 and will not be described herein. From a reading of U.S. Pat. No. 6,402,577, it can be clearly understood that the reciprocal movement of the moveable piston within the hydraulic cylinder causes the steering arm to rotate about the steering axis and, as a result, the outboard motor is rotated about the steering axis. The moveable piston slides axially back and forth within the cylinder and the entire mechanical structure of the steering actuator and the steering arm are conveniently contained within the support structure of the outboard motor.